Agree, the numbers for solar seem exceptionally high… When you say energy payback, do you mean only the avoided cost of producing your own power from solar as opposed to buying it from the grid? That would exclude equipment purchase, installation and maintenance costs, yes? There are commercial sources of hydrogen that’s produced as by-product of large-scale chemical, chlorine production… As a means of storing energy by electrolysis of water, would have to compare its footprint against alternative means of storage, which may well vary from location to location, as well as in terms of absolute cost…ie. stored hydropower vs. battery storage… And as I understand it running methane through fuel cells results in a lot less in the way of CO2 emissions than combusting it… This infographic does come from a fuel cell provider, and needs to be investigated more fully… But to my mind...